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L²-homology and reciprocity for right-angled Coxeter groups

Boris Okun, Richard Scott (2011)

Fundamenta Mathematicae

Let W be a Coxeter group and let μ be an inner product on the group algebra ℝW. We say that μ is admissible if it satisfies the axioms for a Hilbert algebra structure. Any such inner product gives rise to a von Neumann algebra μ containing ℝW. Using these algebras and the corresponding von Neumann dimensions we define L ² μ -Betti numbers and an L ² μ -Euler charactersitic for W. We show that if the Davis complex for W is a generalized homology manifold, then these Betti numbers satisfy a version of Poincaré...

Layer potentials C*-algebras of domains with conical points

Catarina Carvalho, Yu Qiao (2013)

Open Mathematics

To a domain with conical points Ω, we associate a natural C*-algebra that is motivated by the study of boundary value problems on Ω, especially using the method of layer potentials. In two dimensions, we allow Ω to be a domain with ramified cracks. We construct an explicit groupoid associated to ∂Ω and use the theory of pseudodifferential operators on groupoids and its representations to obtain our layer potentials C*-algebra. We study its structure, compute the associated K-groups, and prove Fredholm...

Left quotients of a C*-algebra, III: Operators on left quotients

Lawrence G. Brown, Ngai-Ching Wong (2013)

Studia Mathematica

Let L be a norm closed left ideal of a C*-algebra A. Then the left quotient A/L is a left A-module. In this paper, we shall implement Tomita’s idea about representing elements of A as left multiplications: π p ( a ) ( b + L ) = a b + L . A complete characterization of bounded endomorphisms of the A-module A/L is given. The double commutant π p ( A ) ' ' of π p ( A ) in B(A/L) is described. Density theorems of von Neumann and Kaplansky type are obtained. Finally, a comprehensive study of relative multipliers of A is carried out.

Left-covariant differential calculi on S L q ( N )

Konrad Schmüdgen, Axel Schüler (1997)

Banach Center Publications

We study N 2 - 1 dimensional left-covariant differential calculi on the quantum group S L q ( N ) . In this way we obtain four classes of differential calculi which are algebraically much simpler as the bicovariant calculi. The algebra generated by the left-invariant vector fields has only quadratic-linear relations and posesses a Poincaré-Birkhoff-Witt basis. We use the concept of universal (higher order) differential calculus associated with a given left-covariant first order differential calculus. It turns out...

Les motifs de Tate et les opérateurs de périodicité de Connes

Abhishek Banerjee (2014)

Annales mathématiques Blaise Pascal

Dans cet article, nous définissons une catégorie M o t ˜ C des motifs sur une catégorie monoïdale symétrique ( C , , 1 ) vérifiant certaines hypothèses. Le rôle des espaces sur ( C , , 1 ) est joué par les monoïdes (non necessairement commutatifs) dans C . Pour définir les morphismes dans M o t ˜ C , nous utilisons des classes dans les groupes d’homologie cyclique bivariante. Le but est de montrer que les opérateurs de périodicité de Connes induisent des morphismes M 𝕋 2 M dans M o t ˜ C , où 𝕋 est le motif de Tate dans M o t ˜ C .

L’hyperanneau des classes d’adèles

Alain Connes (2011)

Journal de Théorie des Nombres de Bordeaux

J’exposerai ici quelques résultats récents (obtenus en collaboration avec C. Consani [3], [4], [5], [6]) qui portent sur le cas limite de la “caractéristique 1 ”. Le but principal est de montrer que l’espace des classes d’adèles d’un corps global, qui jusqu’à présent n’a été considéré que comme un espace (non-commutatif), admet en fait une structure algébrique naturelle. Nous verrons également que la construction de l’anneau de Witt d’un anneau de caractéristique p > 1 admet un analogue en caractéristique...

Limit laws for products of free and independent random variables

Hari Bercovici, Vittorino Pata (2000)

Studia Mathematica

We determine the distributional behavior of products of free (in the sense of Voiculescu) identically distributed random variables. Analogies and differences with the classical theory of independent random variables are then discussed.

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